PR tree-optimization/81396

	PR tree-optimization/81396
	* tree-ssa-math-opts.c (struct symbolic_number): Add n_ops field.
	(init_symbolic_number): Initialize it to 1.
	(perform_symbolic_merge): Add n_ops from both operands into the new
	n_ops.
	(find_bswap_or_nop): Don't consider n->n == cmpnop computations
	without base_addr as useless if they need more than one operation.
	(bswap_replace): Handle !bswap case for NULL base_addr.

	* gcc.dg/tree-ssa/pr81396.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@250257 138bc75d-0d04-0410-961f-82ee72b054a4